A quantitative technique for determining lipid A content of endotoxin added to serum has been developed using gas chromatography-mass spectrometry. Future investigation will be directed toward: 1) improving the sensitivity of the present endotoxin assay; 2) quantitation of endotoxin in infected animals with and without antimicrobial therapy; and 3) the interaction of polymorphonuclear white blood cells and endotoxin.